Crucible furnace



Jam 20, 1959 J. D. SELVAGGlo :a1-)AL 2,869,845

v CRUCIBLE FURNACE Filed Oct. 21, 1955 llt United States Patent l2,869,845 CRUCEBLE FURNACE John D. Selvaggio, Pittsburgh, and Calvin C.Wareham, Penn Township, Allegheny County, Pa., assgnors to United StatesSteel Corporation, a corporation of New `lersey Application (lctoher 21,1955, Serial No. 542,065 3 Claims. (Cl. 263-2) This invention relates toan improved Crucible-type laboratory furnace.

Our furnace is especially useful for. preparing samples of iron ore,limestone or the like for analysis of their alkali content. Before suchan analysis can be made, the alkali must be converted to a soluble form.This conversion can be accomplished by fusing the sample withappropriatereagents, such as a mixture of calcium carbonate and ammonium chloride.These materials are fused in an elongated nickel or platinum cruciblewhose bottom is heated to a high temperature, but whose upper portionmust be kept relatively cool to prevent loss of alkali byvolatilization. lOur furnace is used for heating the crucibles in thisprocedure, although obviously it may be used elsewhere where similarproblems are encountered.

An object of our invention is to provide an improved furnace forsupporting and heating elongated crucibles of the aforementioned typeand confining the heat to Where it is actually needed.

A further object is to provide a compact draft-free furnace which canheat a large number of crucibles at a time while maintaining the upperportions of the crucibles relatively cool.

In accomplishing these and other objects of the invention we haveprovided improveddetails of structure, a preferred form of which isshown in the accompanying drawing, in which:

Figure l is a front elevational view, partly broken away, of a furnaceconstructed in accordance with our invention; and

Figure 2 is a vertical section on line Il--ll -of Figure l.

Our furnace comprises a metal frame preferably of welded angle ironconstruction, and a back wall 12, end walls 13 and front wall 14 ofrigid insulating material, such as that sold under the trademarkTransito The fro-nt wall is removably supported on a bracket 15, but theother walls can be permanently aiiixed to the frame 10. The top of thevframe is open. i A manifold 16 is fixed within the frame adjacent thebottom and carries a plurality of Bunsen burners 17, to which it alsosupplies fuel. Adjacent the upper ends of said burners the frame carriesa support 18 on which a plurality of heat shields 19 are mounted, onefor each burner.` Each of said heat shields is a rectangular block ofrigid insulating material which contains an opening to accommodate theburner. The frame also includes an upper pair of downwardly slopingbrackets 2t) and a similar lower pair of such brackets 21.

Either pair of brackets 20 or 21 is adapted to support a removablecrucible rack 22. This rack includes a rigid angle iron frame ofrectangular outline and a plurality of rectangular crucible supportingblocks 23 removably resting in said frame. The blocks 23 correspond withthe respective burners 17 and are of'rigid insulating material. Each hasan opening in which the lower end of an elongated nickel or platinumcrucible 24 can be tted. The upper ends of the crucibles project Wellabove the upper faces of the blocks. When the rack 22 is placed oneither set of brackets 20 or 21, the crucibles lie directly over thecorresponding burners.

-In operation, as applied to preparation of samples for alkalidetermination, mixtures of sample and reagent are placed in thecrucibles 24, which are mounted in the rack 2,869,845 Patented Jan. 20,1959 2 22. First this rack is placed on the upper set of brackets 20.The burners 17 are lighted and the removable front wall 14 installed.The burners are adjusted first to produce a low llame and later a fullflame and held thus for l5 to 20 minutes. Next the burners are turned oiand the rack is lowered to the lower set of brackets 21.

After the front wall is replaced, the burners again arel adjusted tofull ame and heldfthus for about o-ne hour. During each burner operationthe heat shields 19 prevent loss of heat downwardly and protect themanifold 16 against excessive heat. The blocks 23 prevent loss of heatupwardly and maintain the upper portions of the crucibles relativelycool to prevent loss of alkali by volatilization.

While we have shown and described only a single embodiment of theinvention, it is apparent that modifications may arise. Therefore, we donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

We claim:

1. A furnace comprising a frame, walls of insulating material supportedon said frame, a plurality of Bunsen burners mounted in the lowerportion of said frame, means for supplying fuel to said burners,vertically spaced sets of supporting brackets in said frame above saidburners, and a crucible rack adapted to be removably supported on eitherof said sets of brackets, said rack including a rectangular frame and aplurality of blocks of rigid insulating material supported thereon andcorresponding with said burners, each of said blocks having an openingadapted to receive the lower portionv of an elongated crucible forexposure to a different one of said burners, said blocks being adaptedto maintain the upper portions of the crucibles relatively cool.

2. A furnace as defined in claim l including heat shields of rigidinsulating material surrounding each of said burners to prevent downwardloss of heat.

3. A laboratory furnace for fusing samples of iron ore, limestone or thelike preparatory to determination of their alkali content comprising aframe, walls of insulating material supported on said frame, a pluralityof Bunsen burners mounted in the lower portion of said frame, means forsupplying fuel to said burners, upper and lower vertically spaced setsof supporting brackets in said frame above said burners, a crucible rackincluding a rectangular frame and a plurality of blocks of rigidinsulating material supported thereon and corresponding with saidburners, each of said blocks having an opening, elongated cruciblesadapted to receive samples for fusion fitted into the respectiveopenings with their lower ends projecting below said blocks for exposureto said burners and their upper ends being open and projecting above theblocks, said upper brackets being adapted to support said rack duringinitial heating of said crucibles and samples therein, said lowerbrackets being adapted to support said rack during final heating of thecrucibles `and samples, said blocks insulating the upper portions ofsaid crucibles from said burners and thus maintaining the upper portionsrelatively cool to prevent loss of sample through the open ends byvolatilization, and heat insulating shields of rigid insulating materialsurrounding each Iof said burners to prevent downward loss of heat.

References Cited in the le of this patent UNlTED STATES PATENTS 648,655Cushing May l, 1900 824,338 Carey June 26, 1906 2,345,247 Erickson Mar.28, 1944' 2,500,943 Haines Mar. 2l, 1950 2,520,133 Donovan Aug. 29, 1950Y FOREIGN PATENTS 237,397 Great Britain July 30, 1925 522,800 GreatBritain June 27, 1940

